Influence of the Electron-Cation Interaction on Electron Mobility in Dye-Sensitized ZnO and TiO2 Nanocrystals: A Study Using Ultrafast Terahertz Spectroscopy

H. Němec, J. Rochford, O. Taratula, E. Galoppini, P. Kužel, T. Polívka, A. Yartsev, and V. Sundström
Phys. Rev. Lett. 104, 197401 – Published 13 May 2010
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Abstract

Charge transport and recombination in nanostructured semiconductors are poorly understood key processes in dye-sensitized solar cells. We have employed time-resolved spectroscopies in the terahertz and visible spectral regions supplemented with Monte Carlo simulations to obtain unique information on these processes. Our results show that charge transport in the active solar cell material can be very different from that in nonsensitized semiconductors, due to strong electrostatic interaction between injected electrons and dye cations at the surface of the semiconductor nanoparticle. For ZnO, this leads to formation of an electron-cation complex which causes fast charge recombination and dramatically decreases the electron mobility even after the dissociation of the complex. Sensitized TiO2 does not suffer from this problem due to its high permittivity efficiently screening the charges.

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  • Received 18 August 2009

DOI:https://doi.org/10.1103/PhysRevLett.104.197401

©2010 American Physical Society

Authors & Affiliations

H. Němec1,3, J. Rochford2, O. Taratula2, E. Galoppini2, P. Kužel3, T. Polívka4, A. Yartsev1, and V. Sundström1

  • 1Department of Chemical Physics, Lund University, Getingevägen 60, Box 124, 221 00 Lund, Sweden
  • 2Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, USA
  • 3Institute of Physics of the Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Praha 8, Czech Republic
  • 4Institute of Physical Biology, University of South Bohemia, Zámek 136, CZ-373 33 Nové Hrady, Czech Republic

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Issue

Vol. 104, Iss. 19 — 14 May 2010

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